Apparatus and Method for Facilitating a Hydrostatic Pressure Increase in a Fluid Flowing in a Pipe

ABSTRACT

There is described an apparatus ( 1 ) and a method to facilitate a hydrostatic pressure increase in a fluid flowing in a first pipe ( 22 ), where the hydrostatic pressure increase is provided by means of a pumping device ( 3 ) being supplied with energy, the apparatus including: —an energy harvester ( 5 ) arranged to be able to draw a portion of an energy carried by a fluid flowing in a second pipe ( 28 ); and —a mechanical or hydraulic energy transfer device ( 9, 60 ) arranged to be able to transfer a portion of the energy absorbed by the energy harvester ( 5 ) to the pumping device ( 3 ).

The present invention relates to an energy transfer device for fluid inmotion. More particularly the invention relates to an apparatus and amethod for facilitating a hydrostatic pressure increase in a fluidflowing in a first pipe, where the hydrostatic pressure increase isprovided by means of a pumping device being supplied with energy.

The fluid may be a liquid or a gas or a combination thereof.

In processes where there is a need to drive the fluid through a pipe,the fluid is typically driven by means of a pumping device transferringenergy to the fluid so that it for example receives the necessaryhydrostatic pressure increase. Examples of such processes are: coolingsystems in the process industry wherein cooling water is driven throughone or more heat exchangers; water circulation systems for land basedfish farms where fresh seawater is pumped up into a basin and wherecorresponding amounts of water is dumped to sea; and in plantsconverting seawater to freshwater by means of reversed osmosis, where aportion of supplied water is returned to the sea.

Common for the above exemplary processes is that the fluid being“returned” from the process carries energy, which at the present is notutilised to contribute to be able to achieve the desired pressureincrease.

From the publication WO 2008084560 is known an apparatus meant tofacilitate a hydrostatic pressure increase in a fluid flowing in a firstpipe, where the hydrostatic pressure increase is provided by means of apumping device being supplied with energy from an energy harvesterflowing in a second pipe.

From the publications US 2008/0219831 and WO 2007071975 are known energyharvesters arranged for being able to draw a portion of the energy beingcarried by a fluid flowing in a pipe.

The object of the invention is to remedy or reduce at least one of thedisadvantages of the prior art.

The object is achieved by the features disclosed in the belowdescription and in the subsequent claims.

In a first aspect of the present invention there is provided anapparatus to facilitate a hydrostatic pressure increase in a fluidflowing in a first pipe, where the hydrostatic pressure increase isprovided by means of pumping device being supplied with energy, theapparatus including: an energy harvester arranged to be able draw aportion of an energy being carried by a fluid flowing in a second pipe;and a mechanical or hydraulic energy transfer device arranged to be ableto transfer to the pumping device a portion of the energy absorbed bythe energy harvester, the pumping device and the energy harvester beinglocated in a common housing.

Thus, a portion of the energy carried by the fluid in the second pipe isutilised to drive the pumping device. Thereby is required a pump motorwhich only need to be fed an amount of energy corresponding to thedifference between the energy required to pump the fluid to the desiredhydrostatic pressure and the energy being fed to the pumping device fromthe energy harvester.

One type of energy harvester having turned out to be particularly usefulis a so-called differential pressure turbine of the type described inthe Norwegian patents NO 326540 and

NO 325981 whose inventors are the same as in the present invention. Saidpatents relate to an apparatus including two impellers. It is however tobe understood that the apparatus according the present invention mayhave only one impeller. A differential pressure turbine including aso-called lobe pump has in experiments turned out to be very wellsuitable for the purpose.

A lobe pump may also constitute the pumping device of the apparatus.

The energy transfer device may for example be a shaft, a belttransmission or an impeller, all of which provide more or less directcontact between the energy harvester and the pumping device. In thefollowing such transmissions will be denoted mechanical transmissions.

A hydraulic pump known per se may constitute the energy transfer device,the pump being connected to the energy harvester. The hydraulic pump ishydraulically connected to a hydraulic motor known per se arranged to beable to drive the pumping device according to the present invention. Inthe following such a transmission will be called a hydraulictransmission.

A hydraulic energy transfer device may be an alternative to a mechanicalenergy transfer device when the latter is not appropriate or practicallypossible e.g. due to distance and/or obstacles between the energyharvester and the pumping device.

In one embodiment a rigid shaft being common for the pumping device andthe energy harvester constitutes the energy transfer device. Therotational speed of the energy harvester will then be the same as therotational speed of the pumping device. Placing the pumping device andthe energy harvester on a common rigid shaft will be most appropriatewhen the fluid flow speed in the supply line is the same as the fluidflow speed in the return line. The energy that possibly has to be fed tothe pumping device from en external power source such as a power grid isreduced approximately corresponding to the energy transmitted via therigid shaft from the energy harvester.

The common housing in which the pumping device and the energy harvesteraccording to the present invention are located, may be provided with aninlet and an outlet for the first pipe, an inlet and an outlet for thesecond pipe, and an impeller being common for the first pipe and thesecond pipe so that the energy transfer device is constituted by theimpeller. The advantage of this is that the design may be compact andmechanically very simple.

In a second aspect of the present invention there is provided a methodto facilitate hydrostatic pressure increase in a fluid flowing in afirst pipe, where the hydrostatic pressure increase is provided by meansof a pumping device being supplied with energy, where at least a portionof the energy for the pumping device is generated by means of an energyharvester arranged to be able to draw a portion of an energy carried bya fluid flowing in a second pipe, where the energy is transferredmechanically or hydraulically between the energy harvester and thepumping device, and where the energy harvester and the pumping devicebeing located in a common housing.

A third aspect of the invention concerns the use of a pressure reductiondevice allocated to a second petroleum well to drive a pumping deviceallocated to a first petroleum well. The pressure reduction devicecorresponds to the energy harvester discussed under the first and secondaspect of the invention.

In the third aspect the pumping device may be supplied with energy onlyfrom the pressure reduction device. A pump motor driven by electricpower will then not be necessary.

In the following is described an example of a preferred embodimentillustrated in the accompanying drawings, wherein:

FIG. 1 shows a principle sketch of a land-based fish farm whereinseawater is circulated through the fish farm plant;

FIG. 2 shows a principle sketch of a plant where a fluid is supplied toa process unit from a supply line and where two discharge lines extendfrom a downstream side of the process unit;

FIG. 3 shows a principle sketch of two wells where the apparatus of theinvention is used in connection with well control;

FIG. 4 shows a principle sketch of a cooling water plant for processequipment placed onboard an offshore rig, where cooling water is pumpedup from the sea and heat exchanged with a cooling medium onboard the rigbefore the cooling water is returned to sea;

FIG. 5 a shows in a larger scale a view of a combined energy harvesterand pumping device located in a common housing; and

FIG. 5 b shows a cross-section through the line A-A in FIG. 5 a.

Similar or corresponding elements are indicated in the figures with thesame reference numeral.

It is to be emphasized that the figures are only principle sketches andthat mutual proportions between the various elements may be stronglydistorted.

Any position indications such as under, over, lower, upper, right andleft refers to positions that the various elements have in theaccompanying figures.

In the figures the reference numeral 1 denotes an apparatus according tothe present invention. The apparatus 1 includes a pumping device 3connected to an energy harvester 5 and a pump motor 7. The pumpingdevice 3 is connected with the energy harvester 5 by means of connectingdevice 9 being a shaft 9 in the embodiment shown.

The connection is arranged to be able to be selectively broken by a notshown means known per se. It has turned out to be advantageous if theconnection device 9 is provided with a clutch device to thereby be ableto achieve a “soft” connection or disconnection between the pumpingdevice 3 and the energy harvester 5.

The apparatus 1 in FIG. 1 is arranged to be able to pump water from asea 20 through a supply line 22 to a vat 24 placed on a shore 25. Thevat 24 may be such as a basin for farming of aquatic organisms such asfish, mussels or crustaceans.

To provide a possibility for renewal of the water 26 in the vat 24, itis provided with a drain line 28 extending from the vat 24 and back tothe sea 20.

In a fish farm of the type shown, it is normal to pump water from thesea more or less continuously to provide the best possible growing upconditions for the aquatic organisms in the vat 24. Over time the rateof water being supplied to the vat 24 by means of the pumping device 3through the supply line 22 must correspond to the rate of water beingdrained from the vat 24 through the drain line 28.

The water being drained from the vat 24 carries energy. By leading thedrain water through the energy harvester 5, a portion of the energy isdrawn from the drain water and is transferred by means of the shaft 9 tothe pumping device 3. The energy that must be supplied to the pumpingdevice 3 from the pump motor 7 is thereby reduced with a quantitycorresponding to the energy supplied to the pumping device 3 from theenergy harvester 5.

In FIG. 2 the reference numeral 24 indicates a process plant forproviding freshwater from the sea by means of reverse osmosis. Theprocess itself will be well known to a person skilled in the art andwill therefore not be described further here.

Seawater is pumped by means of the pumping device 3 through the line 22into the process plant 24. The flow rate in the line 22 is F1. Seawaterprocessed in the process plant 24 flows out of the process plant 24 intwo lines indicated with the reference numerals 28, 28′. The flow ratein the lines 28, 28′ is F2 and F3 respectively, and their sumcorresponds to the flow rate F1 in the line 22.

The pump 3 may for example be arranged for produce a flow rate F1 of 400l/sec having a liquid pressure of 70 bar. Downstream of the apparatus 24the flow rate F2 may for example be 300 l/sec having a liquid pressureof 70 bar. The flow rate F3 must then be 100 l/sec. The pressure in theliquid flowing in the line 28′ may for example be 1 bar. A personskilled in the art will understand that the liquid in the line 28 isso-called brine, while the liquid in the line 28′ is freshwater.

The pump 3 must transfer relatively large quantities of energy to theseawater being pumped into the process plant 24. In the above examplethe liquid F2 flowing in the line 28 has 75% of the energy of the liquidbeing between the pump 3 and the process plant 24.

To utilise a portion of the energy in the liquid flow F2, the energyharvester 5 is allocated to the line 28.

The energy harvester 5 is mechanically connected to the pumping device 3by means of a rigid shaft 9.

The energy having to be supplied to the pumping device 3 from the pumpmotor 7 is reduced by an amount corresponding to the energy supplied tothe pumping device 3 from the energy harvester 5.

In FIG. 3 is shown a principle sketch of a portion of a first well pipe22 having a first well pressure P_(L) and an adjacent second well pipe28 having a second well pressure P_(H).

In the embodiment the second well pressure P_(H) is too high and has tobe reduced. This is a relatively common situation in the petroleumexploitation industry. The first well pressure P_(L) is however too lowto be able to lift the well stream up to the surface. To remedy thissituation there is a need to reduce the gravity induced pressure drop inthe well.

In the embodiment shown a pumping device 3 is allocated to the firstwell pipe 22 to relieve the static pressure from the fluid column in thewell pipe 22.

The second well pipe 28 is provided with an energy harvester 5. Theenergy harvester 5 may for example be constituted by a differentialpressure turbine having the purpose to reduce the well pressuredownstream of the energy harvester 5, this being achieved by draw energyfrom the well stream. This energy is transferred by means of an energytransmission device 9 to the pumping device 3. In FIG. 3 the energytransmission device 9 is shown as a rigid shaft.

Thus, a pressure-reducing device that is allocated to a second petroleumwell is used to drive a pumping device allocated to a first petroleumwell.

As an alternative to said rigid shaft 9, the energy harvester 5 may beallocated an energy converter (not shown) such as a generator forproducing electric power. The electric power may be transferred via acable to an electric motor allocated to the pumping device 3.

In FIG. 4 is shown a production rig supported by a seabed 30 by means ofa support structure 32. The support structure 32 extends from the seabed30 through a sea surface 20 to the underside of the rig.

The rig is provided with four decks, a lower deck 34, an upper deck 36,a first intermediate deck 38, and a second intermediate deck 38′.

On the lower deck 34, the first intermediate deck 38 and the upper deck36 there is placed a total of four cooling water users all of which, forthe sake of simplicity, being denoted by reference numeral 40. Thecooling water users 40 may for example, but not limited to, be heatexchangers, motors, vanes, process plants or other equipment from whichheat has to be removed.

To supply the cooling water users 40 with cooling fluid, the rig isprovided with a supply line 22 including supply loops 22′. The supplyloops 22′ are fluid-wise connected to each of the cooling water users 40such that cooling water from the supply line 22 is circulated throughthese by means of an apparatus 1 of the present invention.

The apparatus 1 shown in principle in FIG. 4, is of a type wherein apump and an energy harvester are placed in a common housing 53 (see FIG.5B), and wherein an impeller constitutes the energy transfer device. Theapparatus 1 in FIG. 4 is shown in greater detail in FIGS. 5 a andparticularly FIG. 5 b.

To be able to bring cooling water up to the cooling water users 40, avalve 42 is placed in a downstream portion of the supply line 22 afterthe last branch to the supply loops 22′.

The flow direction of the cooling water is shown with arrows.

The cooling water having been supplied with heat from the cooling waterusers 40 flows in the supply loops 22′ to a return or drain line 28.

The drain line 28 is fluid-wise connected to the energy harvester of theapparatus 1. The kinetic energy of the cooling water in the drain line28 as it flows through the energy harvester is transferred via saidimpeller to the pumping device of the apparatus 1.

The energy that has to be supplied from a pump motor 7 to the pumpingdevice of apparatus 1 is thereby reduced with an amount corresponding tothe energy supplied to the pumping device from the energy harvester.

In an end portion 28′ of the drain line 28 the cooling water dischargesfreely over the sea surface 20.

FIG. 5 a shows a side view of an apparatus 1 according to one embodimentof the present invention, but without a possible pump motor which may beconnected to a centrally arranged shaft 61. FIG. 5 b shows a sectionthrough the line A-A in FIG. 5 a.

The apparatus 1 includes a housing 53 provided with two mutually spacedapart parallel bores 52, 58. The bores 52, 58 extend through a chamber55 in the housing 53. The bores 52, 58 are arranged to be connectable tofor example the supply line 22 and the drain line 28 respectively, shownin FIG. 4.

An impeller 60 is rotatably mounted in the chamber 55. The impeller 60includes the central shaft 61. A drum 63 provided with six vanes 65encloses the shaft 61. The vanes 65 are arranged to be able to bedisplaced in a vane chamber 66 formed in the drum 63, in a directiontowards and away from the shaft 61 of the impeller 60. The purpose ofthe displaceable vanes 65 is among other things to provide twoessentially separate chamber portions to thereby limit leaking, via thechamber 55, of fluid flowing in the bores 52, 58.

The movement and guiding of the vanes 65 past the bores 52, 58 may becontrolled in a way known per se, for example as suggested in Norwegianpatent application NO 20092085 appurtenant the present applicant.

To provide a flow F1 through the bore 52, the impeller 60 must besupplied with energy to be set in rotation R. The impeller 60 thusdrives the fluid through the bore 52 and further in for example thesupply line 22 shown in FIG. 4.

A fluid flow F2 being led through the bore 58 from for example the drainline 28 shown in FIG. 4 will contribute to rotation of the impeller 60.

The energy that has to be supplied to the impeller 60 from the motor 7,see for example FIG. 4, to provide the desired flow and hydrostaticpressure increase, is thereby reduced corresponding to the amount ofenergy supplies to the impeller from the fluid flow F2.

The present invention thus provides an apparatus, which in a simplemanner will be able to facilitate hydrostatic pressure increase for afluid flowing in a first pipe, by means of a device utilising energypresent in a second pipe. The apparatus of the invention is simple andmay easily be integrated in already existing piping systems as well asin new piping systems.

1. An apparatus (1) to facilitate a hydrostatic pressure increase in afluid flowing in a first pipe (22), where the hydrostatic pressureincrease is provided by means of a pumping device (3) being suppliedwith energy, the apparatus including: an energy harvester (5) arrangedto be able to draw a portion of an energy carried by a fluid flowing ina second pipe (28); and a mechanical or hydraulic energy transfer device(9, 60) arranged to be able to transfer to the pumping device (3) aportion of the energy absorbed by the energy harvester (5),characterised in that the pumping device and the energy harvester (5)being located in a common housing (53).
 2. An apparatus according toclaim 1, wherein the energy harvester (5) is constituted by a volumetricdifferential pressure turbine.
 3. An apparatus according to claim 1,wherein the energy transfer device (9, 60) is selected from one of or acombination of the group consisting of: a shaft; a belt drive; animpeller; a hydraulic transmission.
 4. An apparatus according to claim1, wherein the housing (53) is provided with an inlet and an outlet forthe first pipe (22), an inlet and an outlet for the second pipe (28),and an impeller (60) being common for the first pipe (22) and the secondpipe (28) such that the energy transfer device (9, 60) is constituted bythe impeller (60).
 5. An apparatus according to claim 1, wherein thefirst pipe (22) is arranged upstream of a process plant (24) for reverseosmosis and wherein the second pipe (28) is arranged downstream of saidprocess plant (24).
 6. An apparatus according to claim 1, wherein thefirst pipe (22) is arranged upstream of a liquid container (24) forstorage of aquatic organisms in a land-based fish farm and wherein thesecond pipe (28) is a drain pipe for said liquid container (24).
 7. Anapparatus according to claim 1, wherein the first pipe (22) is a supplypipe for cooling water for a process plant (40) and the second pipe (28)is a discharge pipe for the cooling water.
 8. An apparatus according toclaim 1, wherein the pumping device (3) is arranged in connection with afirst well pipe (22) having a fluid at a first well pressure and theenergy harvester (5) is arranged in connection with a second well pipe(28) having a fluid at a second well pressure, the first well pressureis less than the second well pressure.
 9. A method to facilitate ahydrostatic pressure increase in a fluid flowing in a first pipe (22),where the hydrostatic pressure increase is provided by means of apumping device (3) being supplied with energy, wherein at least aportion of the energy for the pumping device (3) is generated by meansof an energy harvester (5) arranged to be able to draw a portion of anenergy carried by a fluid flowing in a second pipe (28), where theenergy is transferred mechanically or hydraulically between the energyharvester (5) and the pumping device (3), characterised in that theenergy harvester (5) and the pumping device (3) being located in acommon housing (53).
 10. Use of a pressure reducing device (5) allocatedto a second petroleum well (28) to drive a pumping device (3) allocatedto a first petroleum well (22).